Scanning ion probe systems and methods of use thereof

ABSTRACT

Briefly described, embodiments of this disclosure, among others, include scanning ion probe systems, methods of use thereof, scanning ion source systems, methods of use thereof, scanning ion probe mass spectrometry systems, methods of use thereof, methods of simultaneous ion analysis and imaging, and methods of simultaneous mass spectrometry and imaging.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to copending U.S. Utility applicationentitled “REVERSE-TAYLOR CONE IONIZATION SYSTEMS AND METHODS OF USETHEREOF” to Fedorov et al., filed on date here even with under ExpressMail Label Number EV 628311548 US, which is entirely incorporated hereinby reference.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to ionization systems andmethods.

BACKGROUND

Recent advances in micro/nano fabrication technologies have madepossible the development of a family of scanning ion probes that allowsone to obtain topological, optical, thermal, and (bio)electrochemicalinformation simultaneously, in-situ, and with high spatial and temporalresolution. Integration of the atomic force microscope (AFM) probe withother scanning probes, such as scanning electrochemical microscope(SECM), scanning near-field optical microscope (SNOM), scanning thermalmicroscope.(SThM), and others, produced a unique ability tosimultaneously detect electrical, magnetic, thermal, mechanical,acoustic, and chemical signals. In 1997, Berger et al. introduced theidea of the “lab-on-a-tip” to detect magnetic, electrical, thermal,chemical reaction, stress, and flow signals at the ultimate limits ofsensitivities through the cantilever based scanning probe. [See, Berger,R., Gerber, C., Lang, H. P., and Gimzewski, J. K. Micromechanics: atoolbox for femtoscale science: “towards a laboratory on a tip”,Microelectronic Engineering, 35, 373-379, 1997]. However, thesetechniques have limitations that embodiments of the present disclosureat least partially overcome.

SUMMARY

Briefly described, embodiments of this disclosure, among others, includescanning ion probe systems, methods of use thereof, scanning ion sourcesystems, methods of use thereof, scanning ion probe mass spectrometrysystems, methods of use thereof, methods of simultaneous ion analysisand imaging, and methods of simultaneous mass spectrometry and imaging.

One exemplary scanning ion source system, among others, includes: ascanning ion probe and an ion generation chamber including a membranedisposed at a first end of the ion generation chamber and chamber wallsinterfaced with the membrane, wherein the membrane includes a pluralityof orifices through the membrane, and wherein the scanning ion probe isdisposed adjacent the membrane.

One exemplary method of the disclosure, among others, includes:providing a scanning ion source system; as described herein disposingthe scanning ion probe into a sample, wherein the sample includes anelectrolyte, and wherein the sample is disposed adjacent a sampleelectrode; determining a first location in the sample using the scanningion probe; applying a first voltage to the sample electrode and a secondvoltage to the membrane; ionizing molecules in the sample to produce aplurality of first ionized molecules, wherein the difference between thefirst voltage and the second voltage generates a first potential forcethat drives the first ionized molecules towards the membrane, whereinthe first ionized molecules are from the first location; producing areverse-Taylor-cone of the electrolyte through one or more of theorifices in the membrane, wherein the electrolyte includes the firstionized molecules; and applying a third voltage to an ion generationchamber electrode disposed on a portion of the chamber walls, whereinthe difference between the third voltage and the second voltagegenerates a second potential force that drives the first ionizedmolecules towards a second end of the ion generation chamber.

One exemplary method of the disclosure, among others, includes:disposing a scanning ion probe into a sample, wherein the sampleincludes an electrolyte, wherein the scanning ion probe is disposed on afirst side of a membrane having a plurality of orifices; determining afirst location in the sample using the scanning ion probe; ionizingmolecules in the first location of the sample to produce a plurality offirst ionized molecules, wherein the first ionized molecules aredisposed on the first side of the membrane; producing areverse-Taylor-cone of the electrolyte through one or more of theplurality of orifices in the membrane on a second side of the membraneopposite the scanning ion probe, wherein the electrolyte includes thefirst ionized molecules; generating de-solvated first ionized moleculesfrom the reverse-Taylor-cone of the electrolyte on the second side ofthe membrane; and generating a potential force on the second side of themembrane that drives the de-solvated first ionized molecules away fromthe membrane.

One exemplary scanning ion probe system, among others, includes: anarray of scanning ion sources. Each scanning ion source includes: ascanning ion probe, and an ion generation chamber including a membranedisposed at a first end of the ion generation chamber and chamber wallsinterfaced with the membrane, wherein the membrane includes a pluralityof orifices through the membrane, and wherein the scanning ion probe isdisposed adjacent the membrane.

Other systems, methods, features, and advantages of this disclosure willbe or become apparent to one with skill in the art upon examination ofthe following drawings and detailed description. It is intended that allsuch additional systems, methods, features, and advantages be includedwithin this description, be within the scope of this disclosure, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present disclosure will be more readilyappreciated upon review of the detailed description of its variousembodiments, described below, when taken in conjunction with theaccompanying drawings.

FIG. 1 illustrates a block diagram of an embodiment of a scanning ionprobe system of the present disclosure.

FIG. 2 illustrates an embodiment of a scanning ion probe systemaccording to the present disclosure.

FIGS. 3 and 4 illustrate two additional embodiments of the scanning ionprobe system of the present disclosure.

FIG. 5 illustrates another embodiment of the scanning ion probe systemof the present disclosure in which the sample is a biological cell.

DETAILED DESCRIPTION

Scanning ion probe systems, methods of use thereof, scanning ion sourcesystems, methods of use thereof, scanning ion probe mass spectrometrysystems, methods of use thereof, methods of simultaneous ion analysisand imaging, and methods of simultaneous mass spectrometry and imaging,are disclosed.

The present disclosure includes systems and methods for generation,collection, and detection of ions that are combined with scanning ionprobes (e.g., AFM, SECM, SNOM, SThM, and the like) to enable newanalytical capabilities of the “lab-on-the-tip”. Among numerousapplications in the chemical and materials sciences, the scanning ionprobe systems and methods may be one of the more effective tools forcellular biology and medical research.

In general, embodiments of the present disclosure include a scanning ionprobe and an ion generation chamber that includes a membrane. Thescanning ion probe is disposed adjacent the membrane (e.g., directly orindirectly on the membrane). The membrane includes a plurality oforifices through the membrane. The scanning ion probe and/or themembrane can be introduced to a location in a sample. The sampleincludes an electrolyte, and ions of interest can be generated in thesample, as discussed in more detail below. The scanning ion probe can beused to determine the location of the ion generation chamber in thesample. A reverse-Taylor-cone can be produced through the orifices inthe membrane to disperse the electrolyte as charged droplets (e.g.,containing the ions from the sample) into the ion generation chamber.Although not intending to be bound by theory, these droplets proceedthrough a sequence of desolvation (e.g., solvent evaporation) andelectrical fission events leading to production of disolvated “dry”ions. The ions can then be stored and/or analyzed using one or moretechniques (e.g., mass spectrometry).

By knowing the specific location in the sample of the ion generationchamber using the scanning ion probe, it can be determined that the ionsentering the ion generation chamber are from an area proximate the knownlocation. The spatial extent of this “sampling” area gives the spatialresolution of the device. The sampling area is defined by diffusion andmigration of ions of interest under the influence of the imposedelectric field (expected to be in the range of about 1 to 100 nm) and iscontrolled, at least in part, by the size and/or geometry of thescanning ion probe, the electrolyte composition, and the imposedelectric field. As a result, a simultaneous topographical (e.g.,location) map of the ionic species of the sample (a “topographic map” ofionizable species of the sample) can be obtained. Therefore,simultaneous or substantially simultaneous ion analysis and sampleimaging (or location of the ionized species in the sample) can beconducted, which can be used to identify the component composition of asample at different locations in a sample (e.g., in the x-, y-, and/orz-axis). In an embodiment of the present disclosure, the scanning ionprobe can be combined with other probes to obtain opticalcharacteristics, thermal, characteristics, and the like characteristics,of the sample.

The embodiments of the present disclosure are advantageous in that insitu simultaneous ion analysis and sample imaging can be performed. Forexample, an ion analysis can be conducted for one or more areas of asample to determine the component composition (e.g., chemical and/orbiological composition) of each of the areas. In another example,embodiments of the present disclosure can be used to study complexbiological samples, where the component composition and/or topographycan vary greatly from one area of a sample to another. In anotherexample, embodiments of the present disclosure can be used to studybiological molecules on a single cell basis and/or to study thebiological molecules on the surface of the cell and/or within the cell.In another example, embodiments of the present disclosure can also beused for detection (e.g., via high throughput imaging in the scanningion probe array format) of biochemical molecules that are intrinsicallycharged or that can be externally (e.g., electrochemically) charged(e.g., proteins, DNA, RNA, and the like). Such functionalities would beuseful in analyzing biological tissue constructs, analyzingDNA/RNA/protein gel microarray readouts, screening of tasks, such ascatalyst libraries, and the like.

FIG. 1 illustrates a block diagram of an embodiment of a scanning ionprobe system 10. The scanning ion probe analysis system 10 includes, butis not limited to, an ion collection system 12, a scanning ion sourcesystem 14, and a sample 22. The scanning ion probe analysis system 10can be used to position the ion collection system 12 at a known locationin the sample 22 using the scanning ion probe 18 and to analyze the ionsgenerated from the selected location of the ion collection system 12,all performed simultaneously or substantially simultaneously (within ashort time frame (e.g., microseconds to minutes)). Then, the scanningion probe system 10 can be relocated to another known position orlocation in the sample and can perform a second analysis. In thismanner, a plurality of areas of the sample in the x-, y-, and/or z-axisdirections can be analyzed to obtain an ion “topographic map” of thesample. The map may provide insight into the chemical and/or biologicalspecies located at one or more locations within and/or on the surface ofthe sample.

In another embodiment, a plurality of scanning ion probes (e.g, an arrayof the scanning ion probes) can be used for high throughputapplications. Each scanning ion probe can be operated independently(e.g., in sensing and/or actuation) from the other scanning ion probesand/or operated in unison. Use of an array of independent scanning ionprobes can facilitate analysis of a large area of a sample, and/orfacilitate analysis of a plurality of samples.

The sample 22 can include, but is not limited to, a biological sample(e.g., cells, tissue constructs, DNA/protein microarrays, and the like),a chemical sample (e.g., catalysts, ionic liquids, and the like), andcombinations thereof, disposed in an electrolyte. The electrolyte caninclude, but is not limited to, an electrolytic solution and/orelectrolytic solid/gel. For example the electrolyte can include, but isnot limited to, water, salts, organic solvents (i.e. methanol, toluene,and amines), gel conducting polymer, and combinations thereof. Apotential voltage is applied to the sample to generate ions within theelectrolyte. The ions generated in the electrolyte can subsequently bedirected into the scanning ion source system 14 using another potentialvoltage (e.g., applied to a membrane). In an embodiment, the potentialvoltage can be applied to specific areas of the sample, while not beingapplied to other areas of the sample.

The scanning ion source system 14 can include, but is not limited to, anion generation chamber 16 and a scanning ion probe 18. The scanning ionprobe 18 can be used 30 to determine the position of the ion generationchamber 16 relative to the sample 22 in the x-, y-, and/or z-axis.Therefore, by knowing the position on the sample that the ion generationchamber 16 is proximally located, a determination of the chemical and/orbiological composition of that portion of the sample can be ascertained.The scanning ion probe 18 can include scanning ion probes such as, butnot limited to, an atomic force microscope probe, a scanning tunnelingmicroscope probe, a scanning near field optical microscope probe, ascanning electrochemical microscope probe, a scanning thermal microscopeprobe, and a surface force apparatus probe.

The size and type of the scanning ion probe 18 depends, at least inpart, on the sample to be analyzed, the sample characteristics (e.g.,dielectric vs. conducting, flexible vs. rigid, isothermal vs.non-isothermal, and the like), and the properties of interest to imaging(e.g., topography, florescence, temperature, combinations thereof, andthe like). In an embodiment, the scanning ion probe can be made of orcoated with a dielectric material, or in another embodiment, thescanning ion probe can be made of or coated with a conductive material.For example, the scanning ion probe can be made of or coated with amaterial such as, but not limited to, silicon oxide, silicon nitride,glass, quartz, polymers, metals, carbon, and combinations thereof.Additional details regarding the ion generation chamber 16 are discussedherein.

The ion generation chamber 16 can extract the solvated ions from theelectrolyte and into the ion generation chamber 16. The ion generationchamber 16 can be used to de-solvate the solvated ions and guide them tothe end of the ion generation chamber opposite the membrane or to someother appropriate location. The ion generation chamber 16 can include,but is not limited to, a membrane located at one end of the iongeneration chamber 16, chamber walls with an integrated electrode or anarray of individually-controlled electrodes, and optionally, a heatingelement adjacent the chamber walls to heat the area within the iongeneration chamber 16 to assist in de-solvation.

The shape of the ion generation chamber can vary depending on thespecific application. In general, the ion generation chamber has acylindrical, square, or rectangular geometry. The ion generation chamberhas a length of about 10 nanometers to 100 centimeters and a width ofabout 1 nm to 100 mm. The ion generation chamber can be made ofmaterials such as, but not limited to, conductors, semiconductors, anddielectrics.

The membrane is appropriately interfaced (e.g., electrically isolated)with the chamber walls so that different electric potentials can beapplied to the membrane and/or electrodes of the chamber walls toproduce an appropriate electric field for driving ions via electromotiveforce. The membrane includes a plurality of orifices through themembrane. Upon application of an appropriate electric potential(voltage) to the membrane, a reverse-Taylor cone of the electrolyte iselectrohydrodynamically-induced and extends through one or more of theplurality of membrane orifices into the ion generation chamber 16 toform solvated ions. The reverse-Taylor cone is similar to theconventional Taylor cone used in electrospray, except rather thanspraying a solution out of a capillary tube filled with the electrolytesolution to form a cone and disperse fluid into droplets, the conedescribed herein (shown in FIG. 2) starts outside of the capillary(either at the free surface of the liquid or at each membrane orifice)and then is drawn into the sampling capillary (ion generation chamber)by the electric force exerted on the electrolyte ions upon applicationof appropriate electric field created due to different voltages appliedto the substrate V0, the membrane electrode V1, and the chamber wallelectrodes V2 (See FIG. 2). The formation of the reverse-Taylor cone isdependent, at least, upon the electrolyte, the membrane, the diametersof the orifices, one or more of the applied electric potentials(electrode voltages), the electrode locations, the strength andorientation of the electric field, and the like.

In embodiments having a plurality of independent scanning ion probes,each scanning ion probe can use the same membrane or a differentmembrane. In addition, each scanning ion probe can include its own iongeneration chamber or more than one probe can use the same iongeneration chamber. Various configurations are contemplated and areintended to be included herein although not specifically described.

The membrane can be made of materials such as, but not limited to,metals (e.g., gold, platinum, copper, steel, combinations thereof, andthe like), conductive materials (e.g., polyacetylene and poly(paraphenylene vinylene) (PPV)), combinations thereof, and the like),semiconductor materials (e.g., Silicon (Si), Germanium (Ge), GalliumArsenide (GaAs), combinations thereof, and the like), dopedsemiconductor materials, dielectric materials (e.g., glasses, ceramics(e.g., borosilicate, and alumina or aluminosilicates), various metaloxides (e.g., tantalum oxide, aluminum oxide, silicon oxide,combinations thereof, and the like), polymers (e.g., polyesters/Mylar,Kapton, polycarbonate, combinations thereof, and the like), andcombinations thereof. In an embodiment, the membrane is coated with aconductive material, and the material under the coating may or may notbe conductive (e.g., a dielectric material). In another embodiment, themembrane is formed of or coated with a non-conductive or semiconductivematerial. The size of the membrane orifices is chosen to support anappropriate pressure difference outside (in the sample environment) andinside of the ion generation chamber using capillary forces. In anembodiment, the membrane is a metal wire mesh.

The diameter of the orifices are about 1 nm to 10 mm, about 10 nm to 100μm, and about 100 nm to 10 μm. The membrane can include about 1 to 10¹⁴orifices per square centimeter, about 10 to 10¹⁰ orifices per squarecentimeter, and about 100 to 10⁶ orifices per square centimeter. Thethickness of the membrane can be about 1 nm to 10 mm, about 10 nm to 100μm, and about 100 nm to 10 μm. The diameter of the membrane can be about1 nm to 10 mm, about 10 nm to 100 μm, and about 100 nm to 10 μm.

The ion collection system 12 can be used to collect, guide, and/oranalyze the ions from the ion generation chamber 16. The ion collectionsystem 12 can include, but is not limited to, a mass spectrometrysystem, an ion trapping system, electrochemical (e.g., impedance orredox based) and/or electromechanical (e.g., piezoelectric) sensors,other systems that can be used to analyze ions, and combinationsthereof.

The mass spectrometry system and the ion trapping system can include,but are not limited to, a time-of-flight (TOF) mass spectrometry system,an ion trap mass spectrometry system (IT-MS), a quadrapole (Q) massspectrometry system, a magnetic sector mass spectrometry system, and anion cyclotron resonance (ICR) mass spectrometry system, and combinationsthereof. The mass spectrometry system and the ion trapping system caninclude an ion detector for recording the number of ions that aresubjected to an arrival time or position in a mass spectrometry system,as is known by one skilled in the art. Ion detectors can include, forexample, a microchannel plate multiplier detector, an electronmultiplier detector, or a combination thereof. In addition, the massspectrometry system includes vacuum system components and electricsystem components, as are known by one skilled in the art.

FIG. 2 illustrates an embodiment of a scanning ion probe system. Thescanning ion probe system includes, but is not limited to, the ioncollection system 12, the scanning ion source system 14, and the sample22. The sample 22 includes, but is not limited to, a sample composition32 disposed on or adjacent to a sample electrode 36 (or an array ofelectrodes in an alternative embodiment) in an electrolyte solution 34.The sample electrode 36 is in electrical communication with a voltagesource 38 (V0), which can apply a positive or negative DC potential tothe sample electrode 36. In addition, the voltage source 38 can apply anAC potential to the sample electrode 36. The voltage can range fromabout 0 V to 100 kV, but depends on the sample composition, electrolyte,and the like. The application of the voltage to the sample compositionis performed to generate ions from one or more chemical or biologicalspecies in the sample composition.

The scanning ion source system 14 includes, but is not limited to, ascanning ion probe 52, a membrane 62 having orifices 64, and ion chamberwalls 68. The scanning ion probe 52 is positioned on the membrane 62.The membrane 62 is interfaced with the chamber walls 68. Appropriateelectrical, electric, and/or mechanical structures can be used toconfigure the scanning ion probe 52, the membrane 62, and the chamberwalls 68 to form the scanning ion source system 14. The scanning ionprobe 52, the membrane 62, and the chamber walls 68 are appropriatelyelectrically isolated.

The scanning ion probe 52 can be used to scan in the x- and/or y-axis.In addition, the scanning ion probe 52 can be used to “tap” the sampleby moving in the z-axis direction. For example, “tapping” may bebeneficial when the sample is a biological sample (e.g., a cell).

A membrane voltage source 66 (V1) is in electrical communication withthe membrane electrode 62 and can apply a positive or negative DCpotential to the membrane 62. In addition, the voltage source 66 canapply an AC potential to the membrane electrode 62. The voltage (V1) canrange from about 0 V to 100 kV, but depends on the sample composition,electrolyte phase (e.g., liquid vs. gel/solid) and composition, theelectric potential applied to the other electrodes, and the like. Theapplication of the voltage to the membrane 62 is performed to form thereverse-Taylor cone of the electrolyte through the membrane orifices 64,which draws in the ions generated from the sample composition in theform of solvated ions 44.

An ion chamber electrode or an array of individually-controlledion-guiding electrodes 72 is disposed on portions of the chamber walls68. The ion chamber electrode 72 is in electrical communication with theion chamber voltage source 74 (V2) and can apply a positive or negativeDC potential to the ion chamber electrode array 72. Each electrode inthe array can have a different potential. In an embodiment, the ionchamber voltage source 74 can apply a DC and an AC voltage. The voltagecan range from about 0 V to 100 kV, but depends on the samplecomposition, electrolyte, the electric potential applied to the otherelectrodes, and the like. The application of the voltage to the ionchamber electrode 72 is performed to guide the ions (solvated ions 44and de-solvated “dry” ions 46) from the membrane 62 at the first end ofthe scanning ion source system 14 to the second end of the scanning ionsource system 14 adjacent the ion collection system 12. As mentionedabove, the potential(s) applied to the ion chamber electrode(s) 72depends in part on the potential applied to the membrane 62 and anyelectrodes present in the ion collection system 12 (e.g., ion collectionelectrode 84).

It should be noted that a heating source or element may be used toincrease the temperature in the ion generation chamber 16 to assist inthe de-solvation of the solvated “wet” ions 44 to de-solvated or “dry”ions 46. In short, the reverse-Taylor cone of the electrolyte present inthe ion generation chamber 16 forms solvated ions 44 in drops ofelectrolyte 34. The “wet” ions 44 progress to “dry” ions 46 throughde-solvation processes that are known in electrospray technologies. Thetemperature, pressure, and applied potentials can be used to form “dry”ions 46.

The ion collection system 12 is disposed at the second end of the iongeneration chamber 16 opposite the membrane 62. In another embodiment,the membrane 62 and the ion collection system 12 may not be “in-line” asshown in FIG. 2. The ion collection system 12 can include, but is notlimited to, an interfacing structure 82 and an ion collection electrode84. The interfacing structure 82 can be part of a structure used toconnect the scanning ion source system 14 with the ion collection system12.

The ion collection electrode 84 (e.g., an array of electrodes) is inelectrical communication with an ion collection voltage source 86 (V3),which can apply a positive or negative DC potential to the ioncollection electrode 84. Each electrode in the array can have adifferent potential. In an embodiment, the ion collection electrode 84can apply a DC and/or an AC voltage. The voltage can range from about 0Vto 100 kV, but depends on the sample composition, electrolyte, theelectric potential applied to the other electrodes, the type of the ioncollection system 12, and the like. The application of the voltage tothe ion collection electrode 84 is performed to guide the “dry” ions 46into the ion collection system 12. As mentioned above, the potentialapplied to the ion collection electrode 84 depends, at least in part, onthe potential applied to the membrane 62, the ion generation electrode(array of electrodes) 72, and any electrodes present in the ioncollection system 12 or the scanning ion source system 14.

As mentioned above, the ion collection system 12 can be used to collect,guide, and/or analyze the ions from the ion generation chamber 16. Theion collection system 12 can include, but is not limited to, a massspectrometry system, an ion trapping system, electrochemical sensors,electromechanical sensors, other systems that can be used to analyzeions, and combinations thereof.

The pressure outside the ion generation system 14 (P1), the pressure inthe ion generation system 14 (P2), and the pressure in the ioncollection system 12 (P3) can vary depending, in part, on the ioncollection system 12, the dimensions of the ion generation system 14,the size and shape of the membrane orifices, the electrolyte, the degreeof solvation of the ions entering the ion generation system 14, the modeof the system operation, and the like. P1, P2, and P3 can be about 10⁻¹⁰torr (high vacuum) to 100 times the atmospheric pressure (100*760 torr).In an embodiment, the relative pressures may be the following: P1≧P2≧P3,and it can be controlled by using an external vacuum and/or compressionpumps, proper vacuum isolation fixtures, and in some embodiments, whenthe ion generation chamber is submerged into the electrolyte solution,the size of the membrane orifices may be used to control the pressuredifference between P1 and P2 using the capillary forces at theliquid/membrane interface. Other combinations in relative magnitude ofpressures P1, P2, and P3 can also be envisioned.

FIGS. 3 and 4 illustrate two additional embodiments of the scanning ionprobe system. In FIG. 3, the electrolyte 34 level is raised so thatelectrolyte enters the ion generation chamber 14 through the orifices 64of the membrane 62. It should be noted that the reverse-Taylor cone isstill generated under these conditions.

In FIG. 4, the electrolyte solution 34 level is raised so thatelectrolyte is in contact with the membrane 62, but the electrolyte 34does not enter the ion generation chamber 14 through the orifices 64 ofthe membrane 62. It should be noted that the reverse-Taylor cones arestill generated under these conditions, and they are formed on freesurface of the electrolyte upon application of sufficiently strongelectric field thereby pulling the ions from the solution to the iongeneration chamber.

FIG. 5 illustrates another embodiment of the scanning ion probe systemin which the sample is a cell 102. The scanning ion probe system can beused to obtain and/or analyze, for example, polypeptide and/orpolynucleotide ions. For example, under appropriate conditions, thepolypeptide ions 106 on the surface (membrane) of the cell 102 can bestudied. In addition, under appropriate conditions, the polynucleotideions 104 in the cell 102 can be studied. In an embodiment, the scanningion probe system can be used to study a single biological cell or otherbiological structure (e.g., a virus) at a time in a sample.

Judicious application of the electric potentials V0 and V1 could be usedto selectively pull charged biomolecules (e.g., proteins, DNA, and/orKNA) either from the cell membrane or from the inside of the cell. Bychanging the magnitude of the electric field, cell poration (openingpores in the cell membrane) or lysis (destruction of the cell membrane)can be induced to release the cell content for ionic analysis by theprobe with (lysis) or without (poration) cell death.

While embodiments of the present disclosure are described in connectionwith Example 1 and the corresponding text and figures, there is nointent to limit the disclosure to the embodiments in these descriptions.On the contrary, the intent is to cover all alternatives, modifications,and equivalents included within the spirit and scope of embodiments ofthe present disclosure.

EXAMPLE 1

The following experiments demonstrate that embodiments of the presentdisclosure are capable of reversibly generating charged ions in asample, transporting the ions through a membrane, transporting the ionsin the ion generating chamber, measuring a signal, and scanning modeimaging of different solutions/samples having varying ion concentration(ionic strength) and chemical composition.

The following experiments demonstrate that embodiments of the presentdisclosure are capable of reversibly generating charged ions in asample, transporting the ions through the membrane, transporting theions in the ion generating chamber, measuring a signal, and testing ofdifferent solutions/samples having varying ion concentration (ionicstrength) and chemical composition.

An embodiment of the present disclosure included a cylindrical quartzsampling tube with the metal mesh acting as a membrane 62 and theelectrode 66 (with a plurality of 25 micrometer diameter orifices 64)and the counter (ground) electrode 84 positioned inside of the samplingtube at a controlled distance (via XYZ micrometer stage). The counterelectrode 84 was also connected to a currentmeter with a pre-amplifier,which was used to measure the electric current produced duringexperiments. In this embodiment, the counter electrode 84 alsofunctioned as an ion collection system 12 Detection of the measurablecurrent on the counter electrode and its dependence on the samplingsolution ion composition and probe configuration (e.g., distance betweenthe working and the ground electrodes) is direct evidence of the devicecapabilities as an ion probe system.

The experiments were repeated several times starting from “all equipmentOFF” position. The following is the summary of results. The solutions ofdeionized water, various salts, and MeOH—H₂O-Acetic Acid (varyingconcentration from 0.1 to 1.0%) were used as the ionic buffers in theexperiments.

Effect of the applied potential on the working electrode on iongeneration: When the zero potential (relative to the ground) was appliedto the electrode no measurable current (within the detection systemnoise) was produced regardless of the ionic strength of electrolyte(e.g., from pure dielectric DI water to highly concentrated saltsolution). An increase in the voltage (gradually from 0 V to 500 V to1000 V to 1250 V) applied to the working electrode resulted in asignificant (three or more orders of magnitude increase) in the detectedcurrent (which is a measure of ion generation and transport from theworking electrode to the reference electrode) for the electrolytesolutions. The effect was more significant with an increase in thesolution ionic strength (e.g., when acid concentration was increased),when the mesh electrode was not fully submerged, but in direct contactwith the solution, and when the distance between the working meshelectrode and the reference electrode was the smallest (varied fromabout 3 cm down to about 1 mm). This provides experimental proof ofsuccessful ion generation using reverse-Taylor-cones formed above eachhole in the mesh of the working electrode 66 upon application ofsufficiently strong electric potential relative to the ground(collection) electrode 84.

Effect of the solution composition/ionic strength on ion generation: Thedevice was capable of sensitive detection of a change in the electriccurrent flowing through the ground electrode (device detector) whentesting of the electrolyte solutions/samples with different ionicstrength of electrolyte (accomplished by varying acid concentration inthe MeOH—H₂O-Acetic Acid electrolyte). The experiments were performed ata constant distance mode to eliminate the effect of thebetween-the-electrode distance on the detected electric current. Theexperiments clearly showed an increase in detected ions (current) whileelectrospraying the higher ionic strength sample, and the operation wasreversible (e.g., no hysteresis was observed) when testing was firstperformed of the high ionic strength samples and then the low ionicstrength samples and vice-versa. The same results were observed whensamples of different ionic composition (e.g., different salts) wereanalyzed (imaged) by the device. This demonstrates the capability forelectrospraying samples of different ionic make-up by embodiments of thepresent disclosure.

Effect of the distance between the working electrode and scanned samplesurface (integration of ion generation system with AFM scanning ionprobe): The device was capable of sensitive detection of a change in theelectric current flowing through the ground electrode (device detector)as scanning was performed of the electrolyte solutions/samples atdifferent height above the sample surface. This was controlled by thelarge scale “prototype” of the AFM tip. These results demonstrate thation generation/sampling can be combined with simultaneous topographicalimaging of the sample, for example, using an AFM scanning ion probe orany other “distance-measuring” method.

Although the methodologies of this disclosure have been particularlydescribed in the foregoing disclosure, it is to be understood that suchdescriptions have been provided for purposes of illustration only, andthat other variations both in form and in detail can be made thereuponby those skilled in the art without departing from the spirit and scopeof the present invention, which is defined solely by the appendedclaims.

1. A scanning ion source system, comprising: a scanning ion probe; andan ion generation chamber including a membrane disposed at a first endof the ion generation chamber and chamber walls interfaced with themembrane, wherein the membrane includes a plurality of orifices throughthe membrane, and wherein the scanning ion probe is disposed adjacentthe membrane.
 2. The scanning ion source system of claim 1, wherein themembrane and portions of the chamber walls are at different electricpotentials.
 3. The scanning ion source system of claim 1, wherein an ioncollection system is disposed at a second end of the ion generationchamber.
 4. The scanning ion source system of claim 3, wherein the ioncollection system includes one or more ion collection electrodes.
 5. Thescanning ion source system of claim 3, wherein the ion collection systemincludes a mass spectrometry system.
 6. The scanning ion source systemof claim 5, wherein the scanning ion probe is an atomic force microscopeprobe.
 7. The scanning ion source system of claim 1, wherein thescanning ion probe has a scanning probe surface comprising a dielectricmaterial.
 8. The scanning ion source system of claim 1, wherein thescanning ion probe has a scanning probe surface comprising a conductiveor semi-conducting material.
 9. The scanning ion source system of claim1, wherein the scanning ion probe has a scanning probe surfacecomprising a semi-conducting material.
 10. The scanning ion sourcesystem of claim 1, wherein the scanning ion probe is selected from: anatomic force microscope probe, a scanning tunneling microscope probe, ascanning near field optical microscope probe, a scanning electrochemicalmicroscope probe, a scanning thermal microscope probe, and a surfaceforce apparatus probe.
 11. The scanning ion source system of claim 1,wherein the membrane has a surface comprising a material selected fromthe following: a metal, a conductive material, a semiconductor material,a dielectric material, a polymer, a glass, and combinations thereof. 12.The scanning ion source system of claim 1, wherein the orifices have adiameter of about 1 nanometer to 10 millimeters.
 13. The scanning ionsource system of claim 1, wherein the membrane has a diameter of about 1nanometer to 10 millimeters.
 14. The scanning ion source system of claim1, wherein the membrane has a thickness of about 1 nanometer to 10millimeters.
 15. The scanning ion source system of claim 1, wherein theion generation chamber has a length of about 10 nanometers to 100centimeters.
 16. The scanning ion source system of claim 1, wherein theion generation chamber and the scanning ion probe are movable in adirection selected from: an x-axis, a y-axis, a z-axis, and acombination thereof.
 17. The scanning ion source system of claim 1,further comprising a heating element disposed adjacent the iongeneration chamber.
 18. A method, comprising: providing a scanning ionsource system, comprising: a scanning ion probe; and an ion generationchamber including a membrane disposed at a first end of the iongeneration chamber and chamber walls interfaced with the membrane,wherein the membrane includes a plurality of orifices through themembrane, and wherein the scanning ion probe is disposed adjacent themembrane; disposing the scanning ion probe into a sample, wherein thesample includes an electrolyte, and wherein the sample is disposedadjacent a sample electrode; determining a first location in the sampleusing the scanning ion probe; applying a first voltage to the sampleelectrode and a second voltage to the membrane; ionizing molecules inthe sample to produce a plurality of first ionized molecules, whereinthe difference between the first voltage and the second voltagegenerates a first potential force that drives the first ionizedmolecules towards the membrane, wherein the first ionized molecules arefrom the first location; producing a reverse-Taylor-cone of theelectrolyte through one or more of the orifices in the membrane, whereinthe electrolyte includes the first ionized molecules; and applying athird voltage to an ion generation chamber electrode disposed on aportion of the chamber walls, wherein the difference between the thirdvoltage and the second voltage generates a second potential force thatdrives the first ionized molecules towards a second end of the iongeneration chamber.
 19. The method of claim 18, further comprising:providing an ion collection chamber system at the second end of the iongeneration chamber; applying a fourth voltage to a ion collectionchamber electrode, wherein the difference between the fourth voltage andthe third voltage generates a third potential force that drives thefirst ionized molecules towards the ion collection chamber.
 20. Themethod of claim 19, further comprising: analyzing a mass-to-charge ratioof the first ionized molecules.
 21. The method of claim 20, furthercomprising: moving the scanning ion source system to a second locationin the sample; determining the second location in the sample using thescanning ion probe; applying the first voltage to the sample electrodeand the second voltage to the membrane; ionizing molecules in the sampleto produce a plurality of second ionized molecules, wherein thedifference between the first voltage and the second voltage generatesthe first potential force that drives the second ionized moleculestowards the membrane, wherein the second ionized molecules are from thesecond location; producing a reverse-Taylor-cone from the electrolytethrough the orifices in the membrane, wherein the electrolyte includesthe second ionized molecules; and applying the third voltage to the iongeneration chamber electrode disposed on a portion of the chamber walls,wherein the difference between the third voltage and the second voltagegenerates the second potential force that drives the second ionizedmolecules towards the second end of the ion generation chamber.
 22. Themethod of claim 21, wherein moving is performed in a direction selectedfrom: an x-axis, a y-axis, a z-axis, and a combination thereof.
 23. Themethod of claim 18, wherein the membrane is disposed in the electrolyte.24. The method of claim 18, wherein the electrolyte is disposed in aportion of the ion generation chamber.
 25. The method of claim 18,wherein the membrane is disposed above the electrolyte.
 26. The methodof claim 18, further comprising: heating the ion generation chamber toassist in de-solvation of charged droplets produced from thereverse-Taylor-cone of the electrolyte.
 27. A method, comprising:disposing a scanning ion probe into a sample, wherein the sampleincludes an electrolyte, and wherein the scanning ion probe is disposedon a first side of a membrane having a plurality of orifices;determining a first location in the sample using the scanning ion probe;ionizing molecules in the first location of the sample to produce aplurality of first ionized molecules, wherein the first ionizedmolecules are disposed on the first side of the membrane; producing areverse-Taylor-cone of the electrolyte through one or more of theplurality of orifices in the membrane on a second side of the membraneon the side opposite the scanning ion probe, wherein the electrolyteincludes the first ionized molecules; generating de-solvated firstionized molecules from the reverse-Taylor-cone of the electrolyte on thesecond side of the membrane; and generating a potential force on thesecond side of the membrane that drives the de-solvated first ionizedmolecules away from the membrane.
 28. The method of claim 27, furthercomprising: analyzing a mass-to-charge ratio of the de-solvated firstionized molecules.
 29. The method of claim 28, further comprising:relating an identity of the de-solvated first ionized molecules to thefirst location of the scanning ion probe in the sample.
 30. The methodof claim 27, further comprising: moving the scanning ion probe to asecond location in the sample; determining the second location in thesample using the scanning ion probe; ionizing molecules in the secondlocation of the sample to produce a plurality of second ionizedmolecules, wherein the second ionized molecules are disposed on thefirst side of the membrane; producing a reverse-Taylor-cone of theelectrolyte through one or more of the plurality of orifices in themembrane on the second side of the membrane on the side opposite thescanning ion probe, wherein the electrolyte includes the second ionizedmolecules; generating de-solvated second ionized molecules from thereverse-Taylor-cone of the electrolyte on the second side of themembrane; and generating a potential force on the second side of themembrane that drives the de-solvated second ionized molecules away fromthe membrane.
 31. The method of claim 30, further comprising: analyzinga mass-to-charge ratio of the de-solvated second ionized molecules. 32.The method of claim 31, further comprising: relating an identity of thede-solvated second ionized molecules to the second location of thescanning ion probe in the sample.
 33. A scanning ion probe system,comprising: an array of scanning ion sources, wherein each scanning ionsource includes: a scanning ion probe; and an ion generation chamberincluding a membrane disposed at a first end of the ion generationchamber and chamber walls interfaced with the membrane, wherein themembrane includes a plurality of orifices through the membrane, andwherein the scanning ion probe is disposed adjacent the membrane. 34.The scanning ion probe system of claim 33, wherein an ion collectionsystem is disposed at a second end of the ion generation chamber. 35.The scanning ion probe system of claim 34, wherein the ion collectionsystem includes a mass spectrometry system.